Within the past several years, radio frequency (RF) communication systems have gone from a very limited number of systems, each available for one type of function, to a vast number of potential systems available for providing the same type of basic service. For example, cellular communication systems began in Europe with the Nordic Mobile Telephone (NMT) system. At the time, this was the only system which provided mobile dial-up telephone operations. Since its introduction, newer analog systems have been introduced, such as Total Access Communication System (TACS), and, more recently digital systems such as the Groupe Special Mobile (GSM) (now commonly referred to as the Global System for Mobile communications), DCS-1800 (Digital Cellar System), CT-2 (Cordless Telephone), and DECT (Digital European Cordless Telephone) systems. Further, there are considerable numbers of systems each serving a specific customer service demand such as the European Radio Messaging System (ERMS) for paging and Ministry of Posts and Telecommunications standard MPT 1327 (A Signalling Standard to Trunked Private Land Mobile Radio Systems) for private mobile radio applications. These systems often overlap in their coverage areas. Thereby giving users an option as to which system to select.
There is also a proliferation of new systems being developed, such as the American Digital Cellular (ADC), referred to as Interim Standard 54 (IS-54), and a Personal Digital Cellular (PDC) standard being developed in Japan, referred to as the RCR (Research & Development Center for Radio Systems) standard 27. There is also a Code Division Multiple Access (IS-95) system being developed as a higher capacity/higher quality alternative to the existing systems. In addition to what is normally considered cellular, there are a number of Personal Communication Systems (PCS) and wireless local loop systems being developed that are all competing for customers. Some of these systems will be based on existing protocols (such as the DCS-1900 (Digital Cellular System) being based upon GSM).
Also, some previous land mobile trunking systems are offer dial-up telephony services. One future system currently under design is the Future Land Mobile Public Telephone System (FLMPTS).
However, one problem for the end user is that to be able to go anywhere in the world and use a subscriber unit, the user would need to carry a dozen or more subscriber units since one unit will not operate on all of the systems. By way of example, even though GSM and ADC operate on similar Time Division Multiple Access (TDMA) technologies, there is presently no way to take your GSM phone to America and have it operate on a ADC system.
In addition, even within the same system, the mobile owned by a user may have limitations built in during its original programming that prevent it from using features subsequently developed for a particular system. While there are some subscriber units available today that can be returned and reprogrammed (either electronically or by replacing some of the memory devices containing the programming), the user often finds themselves with a subscriber unit that has become obsolete in just a short time.
A related invention is found in "Bulletin Board Resource for Communication System Access" (U.S. Pat. No. 5,301,359) invented by VandenHuevel et al. and assigned to Motorola Inc. This invention describes a method of providing information regarding communication system capabilities for multiple, independent RF communication systems. The method comprises the steps of monitoring an RF bulletin board that is independent of the multiple, independent RF communication systems; and receiving information from the RF bulletin board regarding the multiple RF communication systems.
Another type of system is described in EP-A2-0 365 200, Majbudar et al. This application describes a telecommunication system in which a subscriber (which includes a touch screen display and a customer premises computer) can, by use of the computer, transmit a request to a central office to provide an appropriate software package to activate a feature of the phone. This application is similar, and in fact uses, a standard ISDN process to transfer a program from one computer to another. The result then is that while certain features in the phone may be activated, it does not address the issue of providing access to multiple communication systems operating using different protocols.